(1) Field of the Invention
This invention relates to an improvement in an apparatus adapted to remove water droplets stuck on the surface of semiconductor material such as semiconductor silicon wafers or glass photomasks by a centrifugal force and to dry the same.
(2) Description of the Prior Art
The above described apparatus is used, after washing the silicon wafers with water, to remove the water and to dry the same. And, this apparatus is constructed of a rotor to be driven and a casing which embraces the rotor. The rotor is provided with one or more holders each adapted to hold a cage-shaped carrier which is adapted to enclose semiconductor material, namely, one or more carrier-holders. Otherwise, a lid centrally defining a gas intake port is provided over the casing while an exhaust port is formed in the circumferential wall of the casing. When the rotor is driven, water droplets present on the surface of the semiconductor material are thrown off by virtue of centrifugal forces applied thereto toward the circumferential wall of the casing. Since a negative pressure is developed at this time in a central region of the rotor, a drying gas such as air or nitrogen gas is sucked into the rotor through the air intake port and is then caused to flow in a circumferential direction through the casing, and is eventually discharged through the exhaust port. The semiconductor material is dried by the gas stream. In particular, this invention is concerned with an improvement in the above apparatus which includes one or two holders. For example, in an apparatus of the prior art which includes only one holder, the holder is disposed in the central region of the rotor. Thus, this apparatus has the defect that water droplets stuck on the portion of the semiconductor material located on the axis of the rotor can not be removed therefrom. On the other hand, turbulence will be caused in the rotor so that a part of the gas may flow back upwardly from the bottom wall of the casing. In some instances, gas streams which flow in the radial direction strike against the circumferential wall, thereby flowing inwardly in the radial direction. Such flows carry water from the circumferential wall and the bottom wall of the casing back onto the semiconductor material and stain the same. Such a prior art apparatus is thus accompanied with drawbacks that such gas flows lower the drying efficiency and reduce the effectiveness of the washing treatment.